1. Field of the Invention
The present invention relates to a circuit for coded symbol conversion, and in particular to such a circuit for converting information resulting from keyboard actuation into coded characters such as may be used in teleprinters.
2. Description of the Prior Art
An international convention has been adopted with regard to teleprinter characters utilizing CCITT Code No. 2 by which certain special characters or symbols are impermissible and therefore cannot be transmitted. Such symbols are, for example, certain German vowels having an umlaut such as a, o and u, as well as symbols representing a paragraph, degrees, exponents, and others. The general practice is to represent these impermissible characters by double or triple characters such as ae, oe and ue in the case of vowels with umlauts and "par" in place of a paragraph sign. German Pat. No. 25 42 864 corresponding to U.S. Pat. No. 4,072,820 discloses and claims a circuit for the generation of double characters of this type following the actuation of an appropriate key on a keyboard. The circuit described therein contains a counter which employs a decoder and a multiplexer to successively check the actuation of the keys which are arranged in the form of a matrix. When a certain key has been actuated, the corresponding count is transferred into a storage. When a key assigned to a double symbol is actuated, the transfer of the count is momentarily blocked and the respective counts assigned to the code characters in the double symbol is awaited. This circuit has the disadvantage of not being useable with commercially available keyboard modules which generate conventional signals following the actuation of a key on the keyboard.